This patch completely replaces the first version of our notebook patch
(gtk-hamann_jeske-980130-0). Unfortunately the first one hasn't been
committed yet, while development continued.

New in this patch :

- The "switch_page" signal was enhanced to also deliver the number of
  the page being switched to.

  Your callback should look like :

  static gint
  your_page_switch_callback (GtkWidget       *widget, 
                             GtkNotebookPage *page, 
                             gint             page_num,
	                     gpointer         data);

- "gtk_notebook_insert_page" now emits "switch_page" when the first
  page gets inserted

The patch is against gtk+-0.99.3.